In CA (Carrier Aggregation) specified up to LTE (Long Term Evolution) Release-10, as shown in (a) of FIG. 5, communications are performed simultaneously by using CC (Component Carrier) #1 and CC#2 under the same radio base station eNB to achieve high throughput.
Meanwhile, in LTE Release-12, “inter-eNB CA (or inter-node UP aggregation)” has been considered (refer to Non-patent document 1) in which CA up to LTE Release-10 is expanded such that, as shown in (b) of FIG. 5, communications are performed simultaneously by using CC#1 and CC#2 under different radio base stations eNB#1 and eNB#2 to achieve high throughput.
The inter-eNB CA needs to be performed to achieve a degree of throughput comparable to LTE Release-10 when, for example, all CCs cannot be accommodated within one radio base station eNB.
The following case is assumed where, in order to perform the inter-eNB CA, a radio base station MeNB may serve as an anchor node to forward data addressed to a mobile station UE and transmitted by a gateway apparatus S-GW to the mobile station UE or a radio base station SeNB, as shown in (a) of FIG. 6.
The following case is assumed where, the gateway apparatus S-GW may serve as an anchor node to forward data addressed to the mobile station UE to the radio base station MeNB or the radio base station SeNB, as shown in (b) of FIG. 6.